Conservation at the Royal Botanic Garden reaps rewards

Conservation at the Royal Botanic Garden reaps rewards

The recent deluge of rain may have been a cause of disappointment for many but for researchers at the Royal Botanic Garden Edinburgh (RBGE), the downpour sparked celebration as their innovative garden project proved its worth.

The experimental Raingarden is a response to rapid climate change and more frequent rainfall where an existing garden was adapted to meet the challenge of heavy rain and subsequently monitor its impact.

Following the downpours earlier this month, the garden successfully absorbed the excess water that fell, reducing floods on nearby paths and capturing rainwater for the benefit of the plants that grow there.

Completed in spring this year, the new Raingarden features a range of carefully selected plants in a special mix of soil, compost, sand and gravel.

The success of the garden could influence the future management of the RGBE and potential planting schemes for coping with climate change.

The Raingarden, that measures 20 metres long by seven metres wide, is a shallow basin that allows water to drain naturally into surrounding ground during heavy rain.

It is located at the lowest elevation of an area known as the Birch Lawn which has suffered historically from waterlogged grass, submerged tree roots and flooded paths.

A selection of Scottish native plants and non-native plants, many of which are known to soak up water and thrive in boggy areas, have been used to create the garden including primulas and hostas as well as the rare and endangered Alpine Sow-thistle Cicerbita alpina which can only be found on four sites in Scotland.

RBGE’s Herbaceous Supervisor Kirsty Wilson, said: “Raingarden creation is great news for plant lovers. Lawns are simply not as effective at soaking up or trapping excess water. Replacing hard surfaces and grass areas with a mixed selection of herbaceous perennials and shrubs can capture water runoff and increase the wildlife and habitat value of the area.”

“The mix of plants we have chosen will encourage a great diversity of wildlife, providing nectar sources for insects and bees in the summer, and we will leave the stems of the perennials and grasses standing over winter to provide a home for invertebrates and food for seed-eating birds.”

Created in collaboration with experts from The Water Academy at Edinburgh’s Heriot-Watt University, the Raingarden is being used as a living laboratory to learn more about the trees, shrubs and wildflowers that are best able to cope with occasional temporary flooding, and can help to naturally reduce waterlogging, as well as plants that can withstand other extreme weather events such as drought.

The Raingarden’s unique bioretention system was created by RBGE horticulturists using the Botanics’ existing soil mixed with compost made on site, sand and fine gravel to a specified particle range size. The composition was specifically developed to allow for water infiltration and retention but also to provide organic material and nutrients to support the plants.

“This experimental garden will be helpful in understanding and planning future site management strategies for coping with an unpredictable, changing climate and ensuring uninterrupted provision of the important public amenity at RBGE.”

Another project with conservation in mind is the RBGE’s efforts to protect some of Scotland’s most vulnerable plant species.

A campaign launched by the garden’s scientists and horticulturalists aims to encourage climbers and walkers to let them know if they spot rare and endangered plants on their travels.

The RGBE team are hoping to receive news of sightings of native species that have been pushed back to remote sites such as Cicerbita alpina or Alpine blue-sow-thistle.

The wider impact of the plant is its role as a barometer for landscape management. Like many rare Scottish plants, it is highly sensitive to grazing, and its future depends on a sustainable approach to the countryside.

The project is part of the Gardens’ commitment to biodiversity and the Global Strategy for Plant Conservation Target 8 which recommends that at least 75 per cent of threatened plant species be growing in safe collections, such as botanic gardens, and at least 20 per cent should be available for recovery and restoration in the wild.

Working in collaboration with Scottish Natural Heritage and landowners monitoring remnant populations of Cicerbita alpina, RGBE scientists collect leaves for genetic analyses and grow plants at their Edinburgh nursery for research and conservation translocations back into their natural environment. Experiments on pollination, pollen and seed quality are undertaken too.

Dr Christopher Ellis, who oversees the project said: “The Alpine blue-sow-thistle had declined to just four populations in Scotland, all located on remote and difficult to access mountain cliffs. Staff from RBGE collected samples of these surviving plants to save the species. The plants are grown at RBGE, where we test their health, focusing on genetics, the ability to produce viable seed and the absence of disease. Three new populations have already been established, more will follow, and we can all have renewed hope for the species’ future in Scotland.

“Anyone who has survived a mountain storm cannot fail to be impressed by the plants and animals clinging to existence under extreme conditions. Such plants face many threats, including climate change.”

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